Enhanced Optimal Torque Control of Fault-Tolerant PM Machine Under Flux-Weakening Operation

This paper describes an enhanced optimal-torque-control strategy for fault-tolerant permanent-magnet (PM) machines under flux-weakening operations. By adjusting the degree of flux weakening according to estimated instantaneous-torque-control errors, the torque-control performance of the machine can be improved when operating above its base speed under either open- or short-circuit fault condition. Extensive simulations under both healthy and fault conditions have been undertaken in order to validate the effectiveness of the proposed control strategy. Experimental results have also been given based on the testing of a prototype five-phase fault-tolerant PM machine.